Apparatus for double-sided grinding

ABSTRACT

A grinding apparatus for machining a workpiece ( 6 ), including an apparatus frame ( 2 ) supporting a grinding station ( 3 ) with a number of grinding heads ( 4 ) with associated grinding elements ( 5 ) arranged such that the grinding elements ( 5 ) are in contact with one surface ( 7 ) of the workpiece at the passage of the workpiece through the grinding apparatus ( 1 ), and an endless conveying means ( 8 ) for the grinding heads ( 4 ), and a roller table ( 9 ) for supporting the workpiece ( 6 ), where the grinding apparatus ( 1 ) includes a further grinding station ( 10 ) with grinding heads ( 4 ) arranged such that the grinding elements ( 5 ) are in contact with the opposite surface ( 11 ) of the workpiece at the passage of the workpiece across the roller table ( 9 ), where the roller table includes a first ( 12 ) and a second set of rollers ( 13 ), and where there is an interspace ( 14 ) between two set of rollers ( 12, 13 ), allowing passage of the workpiece between the two set of rollers ( 12, 13 ), wherein spacing ( 15 ) between individual rollers ( 16 ) in each of the two sets of rollers ( 12, 13 ) is arranged such that a plurality of the rollers ( 16 ) from each of the two sets of rollers ( 12, 13 ) are simultaneously in contact with the opposing surfaces ( 7, 11 ), where a first grinding station ( 3 ) is provided between two succeeding rollers in the first set ( 12 ) and a second grinding station ( 10 ) is provided between two succeeding rollers in the second set ( 13 ).

FIELD OF THE INVENTION

The present invention concerns a grinding apparatus for machining aworkpiece, including an apparatus frame supporting a grinding stationwith a number of grinding heads with associated grinding elementsarranged such that the grinding elements are in contact with one surfaceof the workpiece at the passage of the workpiece through the grindingapparatus, and an endless conveying means for the grinding heads, and aroller table for supporting the workpiece, where the grinding apparatusincludes a further grinding station with grinding heads arranged suchthat the grinding elements are in contact with the opposite surface ofthe workpiece at the passage of the workpiece across the roller table,where the roller table includes a first and a second set of rollers, andwhere there is an interspace between two set of rollers, allowingpassage of the workpiece between the two set of rollers.

BACKGROUND OF THE INVENTION

By industrial grinding or sanding of workpieces that include edges,roundings and surfaces, e.g. table tops or doors or other items withlimited length, and where these edges, roundings and faces are disposedon opposite sides of the workpiece, this will require grinding/sandingof both sides of the workpiece. On conventional grinding apparatuses,this requires two runs through the grinding apparatus in that it isnecessary first to perform grinding of one side of the workpiece, afterwhich the workpiece is turned and the grinding is repeated on the otherside of the workpiece.

The drawback of this is reduced machine capacity and need for increasedhandling of workpieces that require double-sided machining, comparedwith workpieces that only require one-sided machining.

Apparatuses for polishing flat glass plates that are conveyedcontinuously from a production apparatus for glass production are known.Examples of such are known from GB 469951, U.S. Pat. No. 3,036,410, U.S.Pat. No. 3,177,625 and DE 670343. A disadvantage of these apparatuses isthat they are not suited in connection with grinding workpieces withlimited length as the workpiece is not sufficiently supported in orderto avoid substantial deflection during the run until the leading edge ofthe workpiece has passed a grinding station.

OBJECT OF THE INVENTION

It is the object of the present invention to indicate a grindingapparatus that enables grinding of both sides of a workpiece requiringdouble-sided treatment, and which has a limited length such thatgrinding and/or deburring of the workpiece may be completed in one run.

DESCRIPTION OF THE INVENTION

This is achieved by means of a grinding apparatus of the type mentionedin the introduction, which is peculiar in that spacing betweenindividual rollers in each of the two sets of rollers is arranged suchthat a plurality of the rollers from each of the two sets of rollers aresimultaneously in contact with the opposing surfaces, where a firstgrinding station is provided between two succeeding rollers in the firstset and a second grinding station is provided between two succeedingrollers in the second set.

The grinding apparatus is provided with two grinding stations disposedsuch that one grinding station machines one side of the workpiece andthat the other grinding station machines the other, opposite side of theworkpiece. The grinding stations are arranged in series such that theworkpiece is treated by both grinding stations during the passage of theworkpiece through the grinding apparatus. Treatment of both sides of theworkpiece is hereby achieved in one run.

The grinding elements apply a force to the workpiece that necessitatessupport of the workpiece. The roller table functions as this support,but since the grinding elements from the two grinding stations act onthe workpiece with oppositely directed forces, it is necessary with twosets of rollers, one above the other, such that the workpiece issupported in both directions when disposed in the interspace between thetwo sets of rollers. The grinding stations are each disposed betweenrollers on the inlet and outlet sides, respectively, of the workpiece.This ensures effective retention of the workpiece during the entire run.One grinding station is provided between rollers in the first set with aheight of the grinding elements such that they are approximately flushwith a plane tangent to the rollers, and which coincides with the sideof the workpiece facing the grinding elements and thereby worked by thegrinding station. In a corresponding way, the other grinding station isdisposed between rollers in the other set for machining the other sideof the workpiece. The height of the grinding stations in relation to themachined side of the workpiece is significant to the power of thegrinding action, as this determines how strongly the grinding elementsare to press on the workpiece.

It is particularly advantageous to dispose at least two successiverollers opposite each other in each of the two sets of rollers at theinlet side before a grinding element and at least two successive rollersopposite each other in each of the two sets of rollers at the outletside after a grinding element. Consequently, in total at least fourrollers at each their side of a grinding element.

Hereby is achieved that the workpiece is securely supported duringinsertion in the grinding station. When grinding is commenced from theleading edge of the workpiece during a run, the two rollers in each ofthe two sets opposite each other ensure that the workpiece is securelysupported, even though it projects from its clamping between the tworollers in each set. Strong deflection of the workpiece and consequentreduction of the grinding capability is thereby obviated. The leadingedge of the workpiece will, after passage of the grinding element,engage between at least two rollers in each set opposite each other atthe outlet side of the grinding element. Finally, when the trailing edgeof the workpiece loses its engagement with the two rollers in each seton the inlet side of the grinding element, it will still be securelysupported, even though it projects from its clamping between the tworollers in each set at the outlet side of the grinding element.

Such a grinding apparatus may machine workpieces with a limited length.The length of the smallest workpiece to be processed by the grindingapparatus is determined in that the workpiece simultaneously is toengage two rollers from each set opposite each other on at one side ofthe grinding element, and two rollers opposite each other at the otherside of the grinding element, where the last-mentioned rollers are twosingle rollers opposite each other.

Rollers in each of the two sets may be disposed within the grindingstation.

According to a further embodiment, the grinding apparatus according tothe invention is peculiar in that the two rollers in the two set ofrollers are resilient for establishing a squeezing action on theworkpiece. Hereby it becomes possible to retain the workpiece during therun. Another result is that there is still contact between roller andworkpiece, even by workpieces with variations in thickness. Theresilient properties of the rollers have to be adapted to the variationsin thickness that are expected for the workpiece.

According to a further embodiment, the grinding apparatus according tothe invention is peculiar in that the two set of rollers are disposed inapproximately parallel, horizontal planes. This is necessary for theworkpiece to pass through the grinding apparatus without being jammed orchanging its direction.

According to a further embodiment, the grinding apparatus according tothe invention is peculiar in that the rollers in the two set of rollersare disposed opposite each other. Hereby it becomes easier for anoperator to insert the workpiece. Besides, deflection of the workpieceduring passage of the individual rollers is avoided.

According to a further embodiment, the grinding apparatus according tothe invention is peculiar in that the two set of rollers are provided inan arrangement that enables adjustment of the height of the interspacebetween the two set of rollers. If the grinding apparatus is to be usedfor different workpieces, it is suitable to have this adjustmentpossibility as workpieces with different thickness may occur.

According to a further embodiment, the grinding apparatus according tothe invention is peculiar in that the height of the interspace betweenthe two set of rollers is adjusted by means of actuators. By usingactuators for height adjustment of the interspace, limitations caused bythe operators lifting capacity are avoided. If it is necessary with manydaily readjustments of the grinding apparatus to various workpieces,this may occur easily and rapidly by means of actuators. These actuatorsmay be pneumatic, hydraulic or electric.

According to a further embodiment, the grinding apparatus according tothe invention is peculiar in that the rollers are provided with a drivemeans for advancing the workpiece, the drive means optionally being abelt, a toothed belt, a chain or a toothed wheel. The advantage ofproviding the rollers with a drive means is that the operator is not toensure manual advancing of the workpiece during a run through thegrinding apparatus. This makes the grinding apparatus more safe in useand reduces the need for intervention by operators.

According to a further embodiment, the grinding apparatus according tothe invention is peculiar in that a unit for sucking grinding dust isprovided in connection with each grinding station and at each area wherethe grinding elements are in contact with the workpiece. During use ofgrinding apparatuses of the described type, large amounts of grindingdust are released. With consideration to the working environment, thisputs limitations to staying in the vicinity of the grinding machine.Therefore, it is expedient to remove as much as possible of this dust.The disposition of the unit for suction of grinding dust provides thatmost possible dust is removed as it is placed closest to the area in thegrinding apparatus where the dust is generated.

According to a further embodiment, the grinding apparatus according tothe invention is peculiar in that a guide rail for the workpiece isprovided on each suction unit. When the workpiece passes a grinding areawhere also a suction unit is provided, there is no possibility ofsupporting the workpiece. Thus a risk of deflection of the workpiece ispresent. The deflection becomes greater the closer the workpiece comesto the rollers at the outlet side of the grinding station. A guide railis provided before the rollers at the outlet side of the grindingstation in order to avoid jamming of the workpiece and to ensureengagement with the rollers. The guide rail counteracts possibledeflection of the workpiece and disposes it opposite the interspacebetween the two sets of rollers.

According to a further embodiment, the grinding apparatus according tothe invention is peculiar in that the grinding stations are provided inan arrangement that enables adjustment of the height of the grindingelements in relation to the surface of the workpiece, manually or byactuators. Hereby it becomes possible to adjust the grinding effect.This may be particularly advantageous in connection with shiftingbetween coarse and fine grinding and with changing between differentmaterials.

The grinding apparatus may be used for various types of work pieces,such as tabletops, closet doors or similar, and grinding or sanding ofdifferent types of materials such as wood, metal, glass, plastic,composite or similar.

The grinding heads may advantageously be arranged such that thedirection of rotation of two grinding heads in succession is clockwiseand counterclockwise, respectively. Hereby is achieved a very uniformpolishing/deburring. As the grinding heads have separate electricmotors, the direction of rotation may easily be changed for individualgrinding heads.

DESCRIPTION OF THE DRAWING

The invention is explained more closely in the following with referenceto the drawings, where:

FIG. 1 shows a perspective view of a grinding apparatus according to theinvention;

FIG. 2 shows a perspective view of a grinding station;

FIG. 3 shows a side view of the grinding apparatus;

FIG. 4 shows an elementary sketch of the drive system for the rollers;and

FIG. 5 shows a draft of the suction and the guide rail.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a grinding apparatus 1 with an apparatus frame 2 whichincludes a roller table 9 in the entire length of the grindingapparatus, a first grinding station 3 and a second grinding station 10.Each grinding station contains a number of grinding heads 4 withassociated grinding elements 5. The grinding stations are more closelydescribed in connection with the description of FIG. 2.

The workpiece is placed on the roller table 9 for inserting in thegrinding apparatus 1 by an operator 24. The workpiece is supported by afirst set of rollers 12. A second set of rollers 13 retain the workpiecein interaction with the first set of rollers during the run of theworkpiece through the grinding apparatus. The rollers 16 can be providedin an arrangement 17 that enables adjusting the height of the interspacebetween the two sets of rollers 12, 13. The height can be adjustedmanually or by a number of actuators 18. These actuators may e.g. bepneumatic, hydraulic or electric.

The grinding stations 3, 10 are provided in an arrangement 22 that allowvertical adjustment of the grinding stations 3, 10, as thereby allowancecan be made for workpieces with different thickness and differentrequirements to grinding action. The height may be adjusted manually byan operator, or by means of actuators 23 which are preferred due to theweight of the grinding stations. These actuators may also be pneumatic,hydraulic or electric.

On FIG. 2 appears a grinding station 3, 10 free from its apparatusframe. A number of grinding heads 4 with associated grinding elements 5are provided in a roundabout 25 with an endless conveying means 8. Amoving motor with gear 26 drives the grinding heads 4 around thegrinding station while at the same time the grinding elements rotate bymeans of the grinding heads, whereby an epicycloidal movement of theindividual grinding elements 5 is established.

On FIG. 3 is shown a side view of the grinding apparatus 1 with aworkpiece 6 during a run. The grinding apparatus includes a firstgrinding station 3 disposed between the rollers 16 in a first set ofrollers 12 machining one surface 7 of the workpiece, and a secondgrinding station 10 disposed between a second set of rollers 13machining the opposite surface 11 of the workpiece. The grinding heads 4in each grinding station are provided with grinding elements 5 which areadapted to the grinding task. In the shown embodiment, the grindingelements 5 in the first grinding station 3 are of different combination.The height of the interspace 14 between the two sets of rollers 12, 13is adapted to the thickness of the workpiece. The spacing 15 betweenindividual rollers in each set 12, 13 is adapted such that severalsucceeding rollers 16 in each set 12, 13 are in simultaneous contactwith the opposing faces 7, 11 of the workpiece.

FIG. 4 shows the drive mechanism 19 for the two sets of rollers 12, 13.In the shown embodiment, the first set of rollers 12 are driven by abelt. The second set of rollers 13 are freewheeling. The workpiece isdriven forward as the second set of rollers 13 provide retention andensure the required contact between workpiece and the first set ofrollers 12 which rotate. The grinding heads 4 and the grinding elements5 are disposed in an interspace between the one set of rollers 13.

FIG. 5 shows a detail of the grinding apparatus in one of the areaswhere the grinding is performed. A suction unit 20 is provided betweenthe rollers in the first set of rollers 12 and the grinding elements 5are disposed opposite the suction unit 20 between the rollers in thesecond set of rollers 13. A guide rail 21 ensuring engagement betweenthe rollers after workpiece passage of a grinding area is provided atthe outlet side of the suction unit 20.

1. A grinding apparatus for machining a workpiece (6), including anapparatus frame (2) supporting a grinding station (3) with a number ofgrinding heads (4) with associated grinding elements (5), arranged suchthat the grinding elements (5) are in contact with one surface (7) ofthe workpiece at the passage of the workpiece through the grindingapparatus (1), and an endless conveying means (8) for the grinding heads(4), and a roller table (9) for supporting the workpiece (6), where thegrinding apparatus (1) includes a further grinding station (10) withgrinding heads (4) arranged such that the grinding elements (5) are incontact with the opposite surface (11) of the workpiece at the passageof the workpiece across the roller table (9), where the roller tableincludes a first (12) and a second set of rollers (13), and where thereis an interspace (14) between the two set of rollers (12, 13), allowingpassage of the workpiece between the two set of rollers (12 ,13),wherein spacing (15) between individual rollers (16) in each of the twosets of rollers (12, 13) is arranged such that a plurality of therollers (16) from each of the two sets of rollers (12, 13) aresimultaneously in contact with the opposing surfaces (7, 11), that afirst grinding station (3) is provided between two succeeding rollers inthe first set (12) and a second grinding station (10) is providedbetween two succeeding rollers in the second set (13), that the two setsof rollers (12, 13) are provided in an arrangement (17) enablingadaptation of the height of the interspace (14) between the two sets ofrollers (12, 13) and that the height of the interspace (14) between thetwo sets of rollers (12, 13) is adjusted by means of actuators (18). 2.Grinding apparatus according to claim 1, wherein the rollers (16) in thetwo sets of rollers (12, 13) are resilient for establishing a squeezingaction on the workpiece (6).
 3. Grinding apparatus according to claim 1,wherein the two sets of rollers (12, 13) are disposed in approximatelyparallel horizontal planes.
 4. Grinding apparatus according to claim 1,wherein the rollers (16) in the two sets of rollers (12, 13) aredisposed opposite each other.
 5. Grinding apparatus according to claim1, wherein the rollers (16) are provided with a drive means (19) foradvancing the workpiece (6), the drive means optionally being a belt, atoothed belt, a chain or a toothed wheel.
 6. Grinding apparatusaccording to claim 1, wherein that a unit (20) for sucking grinding dustis provided in connection with each grinding station (3, 10) and at eacharea where the grinding elements (5) are in contact with the workpiece(6).
 7. Grinding apparatus according to claim 6, wherein a guide rail(21) for the workpiece is provided on each suction unit (20). 8.Grinding apparatus according to claim 1, wherein the grinding stations(3, 10) are provided in an arrangement (22) that enables adjustment ofthe height of the grinding elements (5) in relation to the surface (7,11) of the workpiece, manually or by actuators (23). 9-10. (canceled)